This invention relates to devices for cutting grooves in concrete. More particularly, this invention relates to concrete groove cutters which travel along the surface of wet or green concrete and use a rotating cutting blade to cut a groove into the surface of the concrete.
Concrete, when poured, is normally viscous, and thus flows and spreads to fill the area it is poured into. Once poured, the concrete will begin to harden in a curing process, until it reaches its typical rock hard state. Between the time the concrete is poured and when the concrete hardens, the concrete will normally be worked or finished to ensure that the surface is smooth and even or has some other discrete surface finish and appearance.
Normally, grooves are cut in the concrete to aid in relieving stresses in the concrete which occur as the concrete shrinks during curing. If grooves are placed only in the surface of the concrete, the grooves provide a weakened plane in which the concrete can crack, thus providing a predicted location of cracks. If the grooves are not provided, the concrete will randomly crack.
Grooves are also often inserted into the concrete surface after it has hardened substantially. This is normally accomplished with large concrete cutting devices which use heavy saws with rotating abrasive blades, and which use water as a coolant to prevent the blade from burning up. These devices are typically very large and heavy, and use large diameter cutting blades varying from 10 to 24 inches in diameter. The resistance on the large blades is so great that the saw will cut a curved path. Sometimes the blade is angled slightly about a vertical axis to cause the saw to cut in a straighter line. Other saws cannot be used until the concrete has hardened substantially, otherwise the finish of the concrete will be marred, the water lubricant will wash the concrete away, and the cutting blade will spall, chip, tear, crack and ravel (hereinafter the term "ravel" or "ravelling" shall include ravelling, chipping, tearing, cracking and spalling) the concrete surface along the groove. The large water lubricated cutting machines which cut the concrete surface after it has substantially hardened often groove the surface after the concrete has experienced significant stresses and cracking. These large machines will also often ravel the surface adjacent the groove.
Several light weight concrete cutting machines have been developed to cut concrete while it is still curing. To reduce the possibility of marring the surface of the wet concrete, these concrete saws have typically been very light weight and use no water lubricant. As a result, they have sacrificed durability. Namely, these saws typically are not heavy duty enough to withstand the rigors of extended use for many hours a day, day after day, for extended periods of time. These saws have typically been of the size that can be hand held, and utilize small motors turning small cutting blades of 4 to 6 inches in diameter which wear quickly. Such saws are described in U.S. Pat. No. 4,869,201.
Therefore there exists a need for a concrete cutting saw which can cut grooves without ravelling in concrete which has not substantially cured so as to incur cracking, and yet which is substantial enough to withstand the rigors of extended use.